The production of spectral colors, primary colors, and thence of mixed colors by means of grating structures has been known for a long time. As representative examples thereof, the references WO 2006/066731 A1, WO 98/23979, or EP 0 585 966 A2 may be cited. All these and still other references of the prior art have in common that the grating structures are produced by laser or electron beam lithography in a relatively soft synthetic substrate. These lithographic methods require multiple and partly complex process steps for producing the grating structures that are well known from the literature.
This applies also for the diffraction-based optical grating structure according to the US 2006/0018021 A1 publication, which discloses an elliptical structure.
A number of application fields are known where optical features are used which have to meet high aesthetic requirements, on one hand, and serve for the authentication of goods, on the other hand. A group of such applications are e.g. packaging foils for cigarettes, foods, or pharmaceuticals, these foils generally being embossed by means of embossing rollers; or the surface of a decorative object, e.g. a part of a watch case, a watchglass of glass or sapphire, or a coin may be the object. Particularly in packaging foils, colored patterns might gain increasing significance if the metallised layer were to be further reduced or entirely omitted. With regard to the aforementioned embossing tools or decorative objects, it is a metal surface that is being structured, and in the case of embossing tools, a hard material layer. This is e.g. disclosed in WO 2007/012215 A1 to the applicant of the present invention.